Memory Management for Systems for Generating 3-Dimensional Computer Images

1. A method for generating 3-dimensional computer images, the method comprising the steps of: subdividing an image into a plurality of tiles; grouping the tiles into a plurality of macrotiles, each macrotile comprising a plurality of the tiles; defining a threshold level for a display list for the macrotiles which is less than the largest allowable display list; loading object data for at least one of the macrotiles into the display list until the threshold level is reached; deriving image data and shading data for each picture element of each of the tiles in at least one of the macrotiles from the object data, wherein the object data for each of the tiles is processed in dependence on the loaded object data having reached the threshold level of the display list; storing the derived image data and shading data in a memory; releasing for further use areas of the display list containing object data used to derive image data and shading data stored in the memory; loading additional object data for at least one of the macrotiles into released areas of the display list; retrieving image data stored in the memory; deriving additional image data and shading data for each picture element of the tiles from the additional object data stored in the display list and the retrieved image data from the memory; storing the additional derived image data and shading data in the memory; and providing shading data stored in the memory for display.

2. The method according to claim 1 , wherein the image data comprises depth data.

3. The method according to claim 1 , wherein the shading data comprises texture data.

4. The method according to claim 1 , wherein the tiles are rectangular regions of predefined and constant size.

5. An apparatus for generating 3-dimensional computer images comprising: at least one processor configured to: subdivide an image into a plurality of tiles; group the tiles into a plurality of macrotiles, each macrotile comprising a plurality of the tiles; load object data for at least one of the macrotile into a display list, the display list having a threshold level which is less than the largest allowable display list; derive image data and shading data for each picture element of each of the tiles in at least one of the macrotiles from the object data, wherein the object data for each of the tiles is processed in dependence on the loaded object data having reached the threshold level of the display list; store the image data and the shading data in a memory; release for further use areas of the display list containing object data used to derive image data and shading data stored in the memory; load additional object data for at least one of the macrotiles into the released areas of the display list; retrieve from the memory stored image data; derive additional image data and shading data for each picture element of the tiles from the additional object data stored in the display list and the retrieved image data from the memory; store the additional derived image data and shading data in the memory; and provide shading data stored in the memory for display.

6. The apparatus according to claim 5 , wherein the image data comprises depth data.

7. The apparatus according to claim 5 , wherein the shading data comprises texture data.

8. The apparatus according to claim 5 , wherein the tiles are rectangular regions of predefined and constant size.

9. A memory management system for use with systems for generating 3-dimensional images, comprising: at least one processor configured to subdivide image data into a plurality of substantially rectangular areas of predefined and constant size; allocate at least one block of storage in a display list to each rectangular area; store in each block data pertaining to surfaces which intersect a respective rectangular area; derive shading data for each picture element of each rectangular area from data in the display list, wherein the data for each rectangular area is processed by a sequence of partial renderings if the amount of the data associated with the rectangular areas exceeds a predetermined number of blocks of storage in the display list; and store the shading data generated by the partial renderings in memory for display; wherein the at least one processor allocates blocks of storage from the display list by determining when the predetermined number of blocks have been used and, in dependence on that determination, causes the supplying of data for deriving the shading data to commence operation, thereby releasing the blocks of storage for additional object data.

10. The system according to claim 9 , wherein the image data comprises depth data.

11. The system according to claim 9 , wherein the shading data comprises texture data.

12. The system according to claim 9 , wherein the tiles are rectangular regions of predefined and constant size.

13. A memory management system for use with systems for generating 3-dimensional computer images, comprising: a memory configured to store object data pertaining to objects in an image which fall in one or more rectangular areas of a plurality of rectangular areas into which the image is subdivided, the memory comprising i) at least one portion allocated to each rectangular area for storing object data pertaining to objects in the respective rectangular area and ii) at least one portion allocated as a global list for storing object data pertaining to objects falling in more than one rectangular area; and at least one processor configured to derive shading data for each rectangular area, from object data for each rectangular area from the respective portion of the memory and, if the rectangular area contains objects also falling in at least one other rectangular area, also from the global list; wherein the shading data derived by the at least one processor is stored for display.

14. The memory management system according to claim 13 , wherein the at least one portion of the memory allocated to each rectangular area and the at least one portion of memory allocated as the global list, are allocated from unused portions of the memory according to requirements, such that the size and location of the at least one portion of the memory allocated to each rectangular area and the size and location of the at least one portion of the memory allocated as the global list, dynamically change as the at least one processor performs its functions.

15. The memory management system according to claim 13 , wherein the global list is arranged to store object data pertaining to objects falling in more than one rectangular area and also object data pertaining to objects falling in a single rectangular area but close to the boundary with another rectangular area.

16. The memory management system according to claim 13 , wherein the shading data comprises texture data.

17. The memory management system according to claim 13 , wherein the rectangular areas are of predefined and constant size.